Sunderland have been forced into a difficult situation with the news that four of their key players are locked in contract disputes with the club.

Sebastian Larsson, Craig Gardner, Jack Colback and Phil Bardsley will all become free agents in the summer if they fail to agree contract extensions.

According to the Daily Mail, both Bardsley and Colback have entered negotiations with the club but are holding out for improved terms to their respective contracts.

Gardner has been linked with a move away from the Stadium of Light on a number of occasions and is not believed to have been offered a new deal, while Larsson is rumoured to be attracting interest from clubs in Italy.

All four players have played a key part in the squad since Gus Poyet took over as Black Cats manager.